At present, large service carriers are attempting to collapse fixed legacy line communications networks into a session initiation protocol (SIP) based network, such as a common Internet protocol multimedia subsystem (IMS) core network. Notably, the service carriers believe a common IMS core network will extend the reach of new multimedia services, increase average revenue per user (ARPU), and reduce the total operating expenses (OPEX) associated with the public switched telephone network (PSTN) core.
However, due to difficulties pertaining to the integration of IMS components with the current legacy access infrastructure, any architecture plan that utilizes the associated legacy access infrastructure is a major deterrent to any IMS network consolidation plan. Although IMS is the preferred target architecture and continual replacement of the current PSTN access infrastructure is not economically feasible, most service carriers want to ensure that any investments made in telecommunications networks are IMS compatible but without completely abandoning the substantial PSTN architecture that still exists. Thus, integrating existing legacy copper lines into an IMS core network without modifying the physical access from these legacy lines would be desirable.
A variety of PSTN emulation system (PES) solutions have been developed in an attempt to provide a solution to the aforementioned dilemma. For example, one such PES architecture proposed involves an IMS PES architecture that interworks H.248 gateways (typically as part of a Multi-Service Access Node (MSAN)) with the IMS core network by way of a functional network element called the Access Gateway Control Function (AGCF). However, this IMS PES solution compels a network carrier to rely on an IMS Telephony Application Server (TAS) to provide fully transparent voice over IP (VoIP) services. Similarly, this IMS PES architecture also introduces some problems with service behavior transparency for the end users depending on the user equipment and subscribed feature set. Namely, a network operator does not want to modify a service set that can alter tariffs associated with end users or subscribers. Services, such as access to 911, lawful intercept, support for coin pay phones, support for conventional POTS phones, and support for TTY phones, are provided in the PSTN. Thus, it would be beneficial to utilize a network element capable of providing legacy devices access to an IMS core network without any modification to legacy access lines located within a traditional PSTN.
Accordingly, in light of these difficulties, a need exists for improved methods, systems, and computer readable media for providing legacy devices access to a SIP based network.